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[thirdparty/man-pages.git] / man3 / tan.3

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk
.\"     <mtk.manpages@gmail.com>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2002-07-27 by Walter Harms
.\" 	(walter.harms@informatik.uni-oldenburg.de)
.\"
.TH TAN 3 2010-09-11 ""  "Linux Programmer's Manual"
.SH NAME
tan, tanf, tanl \- tangent function
.SH SYNOPSIS
.nf
.B #include <math.h>
.sp
.BI "double tan(double " x );
.br
.BI "float tanf(float " x );
.br
.BI "long double tanl(long double " x );
.fi
.sp
Link with \fI\-lm\fP.
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.ad l
.BR tanf (),
.BR tanl ():
.RS 4
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE\ >=\ 600 || _ISOC99_SOURCE ||
_POSIX_C_SOURCE\ >=\ 200112L;
.br
or
.I cc\ -std=c99
.RE
.ad
.SH DESCRIPTION
The
.BR tan ()
function returns the tangent of \fIx\fP, where \fIx\fP is
given in radians.
.SH RETURN VALUE
On success, these functions return the tangent of
.IR x .

If
.I x
is a NaN, a NaN is returned.

If
.I x
is positive infinity or negative infinity,
a domain error occurs,
and a NaN is returned.

If the correct result would overflow,
a range error occurs,
and the functions return
.BR HUGE_VAL ,
.BR HUGE_VALF ,
or
.BR HUGE_VALL ,
respectively, with the mathematically correct sign.
.\" I think overflow can't occur, because the closest floating-point
.\" representation of pi/2 is still not close enough to pi/2 to
.\" produce a large enough value to overflow.
.\" Testing certainly seems to bear this out.  -- mtk, Jul 08
.\"
.\" POSIX.1 allows an optional underflow error;
.\" glibc 2.8 doesn't do this
.\" POSIX.1 an optional range error for subnormal x;
.\" glibc 2.8 doesn't do this
.SH ERRORS
See
.BR math_error (7)
for information on how to determine whether an error has occurred
when calling these functions.
.PP
The following errors can occur:
.TP
Domain error: \fIx\fP is an infinity
.I errno
is set to
.BR EDOM
(but see BUGS).
An invalid floating-point exception
.RB ( FE_INVALID )
is raised.
.TP
Range error: result overflow
.\" Unable to test this case, since the best approximation of
.\" pi/2 in double precision only yields a tan() value of 1.633e16.
.\" .I errno
.\" is set to
.\" .BR ERANGE .
An overflow floating-point exception
.RB ( FE_OVERFLOW )
is raised.
.SH "CONFORMING TO"
C99, POSIX.1-2001.
The variant returning
.I double
also conforms to
SVr4, 4.3BSD, C89.
.SH BUGS
Before version 2.10, the glibc implementation did not set
.\" http://sourceware.org/bugzilla/show_bug.cgi?id=6782
.I errno
to
.B EDOM
when a domain error occurred.
.SH "SEE ALSO"
.BR acos (3),
.BR asin (3),
.BR atan (3),
.BR atan2 (3),
.BR cos (3),
.BR ctan (3),
.BR sin (3)